细菌去除短链氯化石蜡的加压增效作用机制研究

Studying on the efficient removal method for Short chain chlorinated paraffins (SCCPs), which was a newly defined persistent organic pollutant has high economic and social value for ensuring environmental safety and human health. However, there have been not many articles on the removal of SCCPs so far. It can be degraded by selected bacteria, as it known to all that the biological method is an inexpensive but time consuming method. However, proper pressurization can enhance the performance of microbial degradation and removal of pollutants. Thus, the project intends to start from two research points of bacterial screening and pressurization synergism to study the method of efficient removal of SCCPs by bacteria. Firstly, bacteria with removal function on SCCPs are screened via sequencing batch experiments. The effect of factors such as the type of bacteria and the initial concentration of SCCPS was examined. Then pressurized bioreactors are prepared to increase the efficiency of bacterial removal of SCCPs. The influence of different pressures and different internal circulation flow rates was studied. Based on this, the synergistic mechanism of bacterial removal of SCCPs and the interaction between bacterial morphology, the main structural substances (extracellular polymeric substance, cell wall and membrane substances) and SCCPs under pressurized system were further investigated via the use of spectral and energy spectrum. This project will provide new technology and new method for the removal of SCCPs and provide valuable theoretical foundation for removal of SCCPs by bacteria under pressurized system.

短链氯化石蜡（SCCPs）是最新定义的持久性有机污染物。研究高效SCCPs的去除方法，对保障环境安全和人体健康具有较高的经济和社会价值。但目前国内外关于其去除的研究并不多，经筛选的细菌虽对SCCPs有降解作用，但耗时长，基于适度加压有利于微生物降解去除污染物的构想。本项目拟从细菌筛选和加压增效两方面入手来研究细菌高效去除SCCPs的方法。首先通过序批式实验筛选出对SCCPs有去除功能的细菌，考察细菌种类、SCCPs初始浓度等因素的影响，而后用加压生物反应器提高细菌去除SCCPs的效率，考察压力、内循环流速等因素的影响。并在此基础上，借助光谱、能谱等表征手段揭示加压条件下，细菌去除SCCPs的增效作用机制以及细菌形态、主体结构物质（胞外聚合物、细胞壁和膜等物质）与SCCPs的作用机制。本项目的开展将为SCCPs的去除提供新技术和新方法，也为加压体系下细菌去除SCCPs提供有价值的理论基础。

短链氯化石蜡（SCCPs）是2017年新定义的POPs，能在环境中进行迁移转化，能在生物体内积累，并能通过食物链放大，对环境安全和人体健康构成严重威胁。然而现阶段关于SCCPs的去除研究不多，且现行SCCPs去除法中物化处理法成本高、操作条件苛刻，生物处理法耗时长、去除专一性差。因此，研究高效的SCCPs去除方法具有重要现实意义。本项目以SCCPs为研究对象，系统地研究了筛选驯化的细菌对SCCPs的去除性能，并探讨了加压反应器中细菌去除SCCPs的增效机制。.首先，从电子拆解厂周边土壤中通过常规驯化法分离并鉴定了2株对SCCPs具有耐性的细菌，同时从污水处理厂好氧污泥中通过快速筛选得到6株菌，通过16S rDNA基因序列比对，发现土壤的2株菌分别为赖氨酸芽孢杆菌属、不动杆菌属，而污水厂的6株菌分别为大肠杆菌属1-4、克吕沃尔菌属和维氏芽孢杆菌属。随后选取不同种类细菌进行常压去除实验，结果表明去除效果最好的菌是大肠杆菌2，去除率达到了71.52%。用1 g/L乙酸钠培养14天后，发现用该菌降解20 mg/L SCCPs的去除率高达90%，同时，溶液中测得的氯离子含量为11.71 mg/L。.其次，在加压体系下，研究了大肠杆菌2对SCCPs的增效作用机制，重点对比分析了在加压反应器中不同工况下大肠杆菌2对SCCPs的去除性能。结果表明转速对细菌降解SCCPs影响不大，SCCPs浓度对细菌降解SCCPs有影响，当初始浓度从20增加到50 mg/L时，SCCPs的去除率从82.48%降至60.66%。0.15 MPa的适度压力能有效促进细菌去除SCCPs，且纯氧加压优于空气加压，超过此压力，SCCPs去除率明显降低。同时纯氧下的最高脱氢酶活性（DHA）值为0.477 mmol/g VSS（0.15 MPa），适度加压能提高DHA，而超过0.15 MPa的高压力则会抑制DHA。此外胞外聚合物（EPS）的总量随SCCPs的浓度和压力的增大均显著增加，且不同通气类型对EPS影响较大。.最后，通过扫描电子显微镜（SEM）、细胞表面疏水性（CSH）分析和气质联用仪GC-MS，阐明了细菌表面微观形态、细胞主体结构物质与SCCPs的相互作用关系，及细菌降解SCCPs的可能途径。结果表明SCCPs降解的可能途径首先是C-Cl键断裂，脱除Cl-，随后C-C键断裂，长链烷烃降解为短链烷烃。